ref: c9b6c5d5ad8b03e32c0e44959cbb74468dd81cbf
dir: /vpx_dsp/arm/idct4x4_add_neon.asm/
;
; Copyright (c) 2013 The WebM project authors. All Rights Reserved.
;
; Use of this source code is governed by a BSD-style license
; that can be found in the LICENSE file in the root of the source
; tree. An additional intellectual property rights grant can be found
; in the file PATENTS. All contributing project authors may
; be found in the AUTHORS file in the root of the source tree.
;
EXPORT |vpx_idct4x4_16_add_neon|
ARM
REQUIRE8
PRESERVE8
AREA ||.text||, CODE, READONLY, ALIGN=2
INCLUDE vpx_dsp/arm/idct_neon.asm.S
AREA Block, CODE, READONLY ; name this block of code
;void vpx_idct4x4_16_add_neon(int16_t *input, uint8_t *dest, int stride)
;
; r0 int16_t input
; r1 uint8_t *dest
; r2 int stride)
|vpx_idct4x4_16_add_neon| PROC
; The 2D transform is done with two passes which are actually pretty
; similar. We first transform the rows. This is done by transposing
; the inputs, doing an SIMD column transform (the columns are the
; transposed rows) and then transpose the results (so that it goes back
; in normal/row positions). Then, we transform the columns by doing
; another SIMD column transform.
; So, two passes of a transpose followed by a column transform.
; load the inputs into q8-q9, d16-d19
LOAD_TRAN_LOW_TO_S16 d16, d17, d18, d19, r0
; generate scalar constants
; cospi_8_64 = 15137
movw r0, #0x3b21
; cospi_16_64 = 11585
movw r3, #0x2d41
; cospi_24_64 = 6270
movw r12, #0x187e
; transpose the input data
; 00 01 02 03 d16
; 10 11 12 13 d17
; 20 21 22 23 d18
; 30 31 32 33 d19
vtrn.16 d16, d17
vtrn.16 d18, d19
; generate constant vectors
vdup.16 d20, r0 ; replicate cospi_8_64
vdup.16 d21, r3 ; replicate cospi_16_64
; 00 10 02 12 d16
; 01 11 03 13 d17
; 20 30 22 32 d18
; 21 31 23 33 d19
vtrn.32 q8, q9
; 00 10 20 30 d16
; 01 11 21 31 d17
; 02 12 22 32 d18
; 03 13 23 33 d19
vdup.16 d22, r12 ; replicate cospi_24_64
; do the transform on transposed rows
; stage 1
vmull.s16 q15, d17, d22 ; input[1] * cospi_24_64
vmull.s16 q1, d17, d20 ; input[1] * cospi_8_64
; (input[0] + input[2]) * cospi_16_64;
; (input[0] - input[2]) * cospi_16_64;
vmull.s16 q8, d16, d21
vmull.s16 q14, d18, d21
vadd.s32 q13, q8, q14
vsub.s32 q14, q8, q14
; input[1] * cospi_24_64 - input[3] * cospi_8_64;
; input[1] * cospi_8_64 + input[3] * cospi_24_64;
vmlsl.s16 q15, d19, d20
vmlal.s16 q1, d19, d22
; dct_const_round_shift
vrshrn.s32 d26, q13, #14
vrshrn.s32 d27, q14, #14
vrshrn.s32 d29, q15, #14
vrshrn.s32 d28, q1, #14
; stage 2
; output[0] = step[0] + step[3];
; output[1] = step[1] + step[2];
; output[3] = step[0] - step[3];
; output[2] = step[1] - step[2];
vadd.s16 q8, q13, q14
vsub.s16 q9, q13, q14
vswp d18, d19
; transpose the results
; 00 01 02 03 d16
; 10 11 12 13 d17
; 20 21 22 23 d18
; 30 31 32 33 d19
vtrn.16 d16, d17
vtrn.16 d18, d19
; 00 10 02 12 d16
; 01 11 03 13 d17
; 20 30 22 32 d18
; 21 31 23 33 d19
vtrn.32 q8, q9
; 00 10 20 30 d16
; 01 11 21 31 d17
; 02 12 22 32 d18
; 03 13 23 33 d19
; do the transform on columns
; stage 1
vadd.s16 d23, d16, d18 ; (input[0] + input[2])
vsub.s16 d24, d16, d18 ; (input[0] - input[2])
vmull.s16 q15, d17, d22 ; input[1] * cospi_24_64
vmull.s16 q1, d17, d20 ; input[1] * cospi_8_64
; (input[0] + input[2]) * cospi_16_64;
; (input[0] - input[2]) * cospi_16_64;
vmull.s16 q13, d23, d21
vmull.s16 q14, d24, d21
; input[1] * cospi_24_64 - input[3] * cospi_8_64;
; input[1] * cospi_8_64 + input[3] * cospi_24_64;
vmlsl.s16 q15, d19, d20
vmlal.s16 q1, d19, d22
; dct_const_round_shift
vrshrn.s32 d26, q13, #14
vrshrn.s32 d27, q14, #14
vrshrn.s32 d29, q15, #14
vrshrn.s32 d28, q1, #14
; stage 2
; output[0] = step[0] + step[3];
; output[1] = step[1] + step[2];
; output[3] = step[0] - step[3];
; output[2] = step[1] - step[2];
vadd.s16 q8, q13, q14
vsub.s16 q9, q13, q14
; The results are in two registers, one of them being swapped. This will
; be taken care of by loading the 'dest' value in a swapped fashion and
; also storing them in the same swapped fashion.
; temp_out[0, 1] = d16, d17 = q8
; temp_out[2, 3] = d19, d18 = q9 swapped
; ROUND_POWER_OF_TWO(temp_out[j], 4)
vrshr.s16 q8, q8, #4
vrshr.s16 q9, q9, #4
vld1.32 {d26[0]}, [r1], r2
vld1.32 {d26[1]}, [r1], r2
vld1.32 {d27[1]}, [r1], r2
vld1.32 {d27[0]}, [r1] ; no post-increment
; ROUND_POWER_OF_TWO(temp_out[j], 4) + dest[j * stride + i]
vaddw.u8 q8, q8, d26
vaddw.u8 q9, q9, d27
; clip_pixel
vqmovun.s16 d26, q8
vqmovun.s16 d27, q9
; do the stores in reverse order with negative post-increment, by changing
; the sign of the stride
rsb r2, r2, #0
vst1.32 {d27[0]}, [r1], r2
vst1.32 {d27[1]}, [r1], r2
vst1.32 {d26[1]}, [r1], r2
vst1.32 {d26[0]}, [r1] ; no post-increment
bx lr
ENDP ; |vpx_idct4x4_16_add_neon|
END